Class Notes Standards Addressed:

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1 Name: Period #: Class Notes Standards Addressed: History of the Periodic Table: Demitri Mendeleev = Russian chemist who discovered a pattern to the in o How did he discovery a pattern to the elements? First, he wrote the names and of the elements on cards. Then, he arranged his cards by different properties, such as density, appearance, and point. Finally, a patterned appeared when he arranged the elements in order of increasing mass. He found that elements with similar properties occurred in a repeating pattern. That is, the pattern was periodic. Periodic = describes something that occurs or at regular intervals. He found that the elements properties followed a pattern that repeated every seven elements. His table became known as the periodic table of the elements. o There were gaps in Mendeleev s Periodic Table. He predicted that there were yet to be discovered elements that would fill these gaps. He used the pattern to predict their. By 1886, all the gaps had been filled and his predictions were correct. o There were still a few elements properties that did not fit the pattern in Mendeleev s table. In 1914, Henry Moseley, determined the number of protons the number of an atom. All elements fit the pattern in Mendeleev s periodic table when they were arranged by. o All of the more than 30 elements discovered since 1914 follow the periodic law. Periodic Law = states that the repeating and physical properties of elements change periodically with the atomic numbers of the elements.

Finally, a patterned appeared when he arranged the elements in order of increasing mass. He found that elements with similar properties occurred in a repeating pattern.

2 Name: Period #: Class Notes Standards Addressed: Periods: Groups: Exceptions: Period = in chemistry, a horizontal row of elements in the periodic table. o All of the elements in a period have the same number of atomic orbitals. Every element in the top row (the first period) has one orbital for its electrons. All of the elements in the second row (the second period) have two for their electrons. At this time, the maximum number of electron orbitals for any element is. Group = a vertical column of elements in the periodic table; elements in a group share chemical and properties. For this reason, a group can also be called a family. o The elements in a group have the same number of electrons in their outer orbital. Electrons in the outer orbital are called valence. Every element in the first column (group one) has one electron in its outer shell. Every element on the second column (group two) has electrons in the outer shell. There are some exceptions to the order when you look at the transition elements, but you get the general idea. Hydrogen can have the talents and electrons of two groups, one and seven. Helium is different from all of the other elements. It can only have two electrons in its outer shell. Even though it only has two, it is still grouped with elements that have eight because of its properties.

All of the elements in the second row (the second period) have two for their electrons. At this time, the maximum number of electron orbitals for any element is.

3 We can divide the periodic table into two sections of elements: 1. (Groups 1-2 & 13-18) 2. (Groups 3-12) According to their properties, all elements of the Periodic Table are classified as: Metals, Nonmetals, and Metalloids Metals (90 total): Properties o Shiny o Most are ductile = can be drawn into thin wires o All are good conductors of electric currents o Most are malleable = can be flattened with a hammer o Most are good conductors of thermal energy o Most are at room temperature Found on Periodic Table o Left of the zigzag line Nonmetals (17 total): Properties o Not ductile o Not malleable o Not shiny o conductor of electric current o conductor of thermal energy o More than half are gases at room temperature Found on the Periodic Table o Right of the zigzag line o Atoms of most nonmetals have an almost complete set of in their outer orbital (complete set = 8 electrons) o Includes noble gases (group 18) which have a complete set of electrons Metalloids (7 total): Properties o Some are shiny o Some are not malleable they are brittle o Some are hard o Semiconductors some are good conductors of electric current Found on the Periodic Table

drawn into thin wires o All are good conductors of electric currents o Most are malleable = can be flattened with a hammer o Most are good conductors of thermal energy o Most are at room temperature

solids Low Low Increase in from top to bottom Group II: Alkaline-Earth Metals

4 o Border the zigzag line o Atoms have about half of a complete set of electrons in their outer energy level or Group I: Alkali Metals Silvery solids Low Low Increase in from top to bottom Group II: Alkaline-Earth Metals Denser and harder than alkali metals melting points, but not as reactive as alkali metals

5 Group 17: Halogens All (except Astatine-radioactive metalloid) Form salts with Group 18: Noble Gases Rarely combine with other Very low Glow when exposed to electricity Transition Elements: Metals Higher than representative elements (except Mercury)

other Very low Glow when exposed to electricity Transition

6 Reading the Elements: Of the 114 elements discovered so far only 92 occur naturally. The remaining 12 have to be made in the laboratory and are radioactive. o The table below doesn t show all 114, but your book does.

7 Reading the Elements of the Periodic Table: 4 parts o Chemical Symbol o Atomic Mass o Atomic Number o Element name

Section 1: Arranging the Elements Pages 106-112

Study Guide Chapter 5 Periodic Table Section 1: Arranging the Elements Pages 106-112 DISCOVERING A PATTERN 1. How did Mendeleev arrange the elements? a. by increasing density b. by increasing melting point